Born and raised in vegas, so I can help you out.
Fisrt off, if you push your trip back a month you can most likely save a lot of money. September is still hot as balls and still prime tourist time so hotel rates will be higher and you will sweat your ass off. Mid-October begins the "off season" if there is one in vegas you can probably save some dough on rooms. However, I've heard they're desperate to fill rooms at this point so you may be able to get a deal anytime.
As far as playing cards go, there are a few ways to look at it-
The strip casinos have poker rooms packed with tourists that watched the WSOP on ESPN and think they're going to win a million. These rooms are packed with drunken idiots with pockets full of cash, but there will be a few sharks in there taking everyone's money. You may have to wait a long time to get a table, especially if you want to play with four friends. If you are good at poker and want some idiots to take money from but don't mind the wait, hit the strip casinos (Rio, Excalibur, MGM, NY NY, Planet Hollywood etc. etc.)
Good poker rooms, shouldn't be a wait unless there's a tournament. More relaxed environment but with all the debauchery you can handle. Less drunken idiots, more locals who think they're proffesional gamblers (they're not) but still good games. If you just want to hang with your boys and play some cards I recommend this route. (GV Ranch, Sam's Town, Boulder Station, etc. etc. Just make sure its not a dump because there are a few of those- you can check with me if you like)
*the only draw back with off striup places is that, well, you're off the strip. Some places are pretty far away from the strip too ($20 cab ride?). If you don't care about the touristy stuff its cool but if you want to hit the clubs every night it could get pricey.
Downtown (old vegas)
and1mcgee is right sorta, there are a few good places to play in old vegas. But you don't want to stay there (unless you need a crack fix I guess). The few good places are near fremont street but its a rough part of town no matter how much they polish that turd. I'd say be careful if you go down there, stay on the beaten path and don't talk to strangers with knives. The Golden Nugget is a really cool place if you do go down there, then there's the fremont street experience that has a lot of casinos right there that you can play at. Same caveats as a strip casino poker room apply, though.
If you're ballin out of control and bling blingin and whatnot you can hit the upscale joints (palazzo, bellagio, palms etc). But if you have cash to spare in vegas then you don't need my help. I included the palms here because its poker rooms are high limit. Lots of money in those rooms and it is too rich for my blood. Palms is the hot spot to go though and I'd recommend going there if you want to party. Good clubs and REALLY REALLY REALLY hot scandalous women. Playboy club is a must see as well.
Let me know if I can answer any questions or help out with a recommendation.
10 tm H2H Dynasty (3rd Year)
7X7 + TB, OPS & Holds, QS
OF-(start 3) Braun, C. Davis, Kemp, Marte, Cuddyer
UTIL- Votto, one of the above OF
Bench- 1 spot for a hot-schmotato
SP- Greinke, Latos, M. Moore, Medlen, Iwakuma, Hamels, Gausman, E. Ramirez, H. Bailey, T. Walker, J. Tallion, M. Pineda, I. Nova
RP- A. Reed, R. Soriano, G. Holland, Balfour, D. Smyly
DL- B. Beachy